An inkjet printing system typically includes one or more printheads and their corresponding ink supplies. Each printhead includes an ink inlet that is connected to its ink supply and an array of drop ejectors, each ejector consisting of an ink pressurization chamber, an ejecting actuator and a nozzle through which droplets of ink are ejected. The ejecting actuator may be one of various types, including a heater that vaporizes some of the ink in the pressurization chamber in order to propel a droplet out of the orifice, or a piezoelectric device which changes the wall geometry of the chamber in order to generate a pressure wave that ejects a droplet. The droplets are typically directed toward paper or other recording medium in order to produce an image according to image data that is converted into electronic firing pulses for the drop ejectors as the recording medium is moved relative to the printhead.
A common type of printer architecture is the carriage printer, where the printhead nozzle array is somewhat smaller than the extent of the region of interest for printing on the recording medium and the printhead is mounted on a carriage. In a carriage printer, the recording medium is advanced a given distance along a media advance direction and then stopped. While the recording medium is stopped, the printhead carriage is moved in a direction that is substantially perpendicular to the media advance direction as the drops are ejected from the nozzles. After the carriage has printed a swath of the image while traversing the recording medium, the recording medium is advanced; the carriage direction of motion is reversed; and the image is formed swath by swath.
The ink supply on a carriage printer can be mounted on the carriage or off the carriage. For the case of ink supplies being mounted on the carriage, the ink tank can be permanently integrated with the printhead as a print cartridge so that the printhead needs to be replaced when the ink is depleted, or the ink tank can be detachably mounted to the printhead so that only the ink tank itself needs to be replaced when the ink tank is depleted. Detachably mounted ink tanks for a carriage printer typically contain only enough ink for up to about several hundred prints. This is because the total mass of the carriage needs be limited so that accelerations of the carriage at each end of the travel do not result in large forces that can shake the printer back and forth. As a result, users of carriage printers need to replace carriage-mounted ink tanks periodically depending on their printing usage, typically several times per year. Consequently, the task of replacing a detachably mounted ink tank in the holding receptacle should be simple and reliable. Ink tanks can contain a single color ink, or they can have several ink chambers each containing a different color ink that is supplied to the printhead through a corresponding outlet port.
Inkjet ink includes a variety of volatile and nonvolatile components including pigments or dyes, humectants, image durability enhancers, and carriers or solvents. For proper operation of the inkjet printhead it is important that the ink transferred from the outlet port of the ink tank to the inlet port of the printhead have the appropriate balance of these ink components. Therefore, during shipping and storage of an inkjet ink tank it is common practice to provide a seal over the outlet port(s) of the ink tank in order to inhibit the evaporative loss of the volatile components of the ink. U.S. Pat. No. 6,464,339 discloses a removable seal that is adhesively attached over the outlet port of an ink tank. US Published Patent Application 2008/0204524 discloses a sealing device including a compliant sealing member and a retainer having a latching feature to facilitate latching of the sealing device to an ink tank and also a protective region for protecting a circuit device on the ink tank. The background section of US Published Patent Application 2009/0251514 describes seals that are attached to the ink tank by ultrasonic welds, heat stakes or mounting hardware. An advantage of ultrasonic welds holding a sealing member in place is that the seal can be made more impervious to evaporative loss of volatile components of the ink. However, particularly for ink tanks including a plurality of outlet ports, the number and extent of ultrasonic welds can require the user to apply a significant force to break the welds in order to remove the seal prior to installing the ink tank into the printhead.
What is needed is a seal and seal retainer for an ink tank that is highly effective in preventing evaporative loss of volatile ink components but enables the user to apply the force required in an easy and well-controlled fashion for breaking the weld joints that hold the seal in place.